The National Insurance number is a number used in the United Kingdom in the administration of the National Insurance or social security system. It is also used for some purposes in the UK tax system.
The number is sometimes referred to with the abbreviations NI No or NINO.
Allocation of number
3 months before a person's 16th birthday, HM Revenue and Customs (HMRC) notifies them of their NI number.
In 1993, a one-off mass allocation of NI numbers was made to all children under the age of 16 whose parents were in receipt of Child Benefit. As a result of this, siblings who met the criteria above were allocated NI numbers sequentially.
People from abroad who wish to work in the UK, or those to whom a number was not initially allocated as children, must apply for a number through the Department for Work and Pensions (DWP).
Format
The format of the number is two prefix letters, six digits and one suffix letter. An example given at the source is QQ123456C, although that is an invalid entry according to the definition.
Neither of the first two letters can be D, F, I, Q, U or V. The second letter also cannot be O. The prefixes BG, GB, NK, KN, TN, NT and ZZ are not allocated. Validation lists of issued two-letter prefixes are published from time to time.
After the two prefix letters, the six digits are issued sequentially from to . Since 2009, the last two digits determine the day of the week on which various social security benefits are payable and when unemployed claimants need to attend their Jobcentre to sign on (renew their claims): 00 to 19 for Monday, 20 to 39 for Tuesday, 40 to 59 for Wednesday, 60 to 79 for Thursday and 80 to 99 for Friday.
The suffix letter is either A, B, C, or D. The NI number is unique without the suffix letter, so, for example, if exists, then there will be no other numbers beginning with (although temporary numbers were not necessarily unique, because two people with the same date of birth would have had the same number). In official electronic submissions, the final letter may be represented by a space if not known.
The Northern Ireland National Insurance scheme is funded and administered separately from the scheme in Great Britain but operates identically so that, in practice, the same rules apply throughout the United Kingdom.
History
Until 1975, the suffixes A, B, C and D at the end of the NI number signified the period of validity of the National Insurance cards originally used to collect National Insurance contributions (NICs). Cards were exchanged every twelve months and because of the very large numbers of cards issued the exchange was staggered.
Suffix A cards ran from March of one year until March of the next when they were exchanged for a new one. Suffix B suffix cards ran from June until the following June, suffix C from September until the following September and suffix D from December until the following December. For example, a B stagger card issued in 1955 might have run from the first Monday in June that year until the first Sunday in June the following year.
This staggered system operated from 5 July 1948 until 1975, at which time the A stagger cards were extended to run an extra five weeks, until 5 April 1975, in line with the end of the tax year. The B, C and D stagger NI Cards had a shorter period of validity in their final year and ran from June, September and December respectively in 1974 until 6 April 1975. From 6 April 1975 onwards, a computerised National Insurance Recording System (NIRS) was used to allocate all NICs by tax years.
In Great Britain, expired NI cards were sorted into one hundred separate groups corresponding to the final two numbers of the NI number and were posted to the individual insured person's NI account (the RF1) by the corresponding one hundred ledger sections at the Records Branch of the Central Office of the Ministry of National Insurance and its successors.
These sections dealt not only with the recording of NI contributions but with requests for information about qualifying contributions necessary to pay sickness, unemployment, widows, and other benefits and also with any correspondence arising from those NI accounts and NI cards. Within each of the sections, NI numbers were allocated among 16 splits with one clerk administering each split. To trace unknown NI numbers, a general index contained millions of small RF2 index slips, filed in order of surname and listing the name(s), date of birth, and NI number for every person within the National Insurance scheme.